(Exchange) (Step) (Waltz)
by meggannn
Summary: There'd been music, really, and dancing, ever since John walked into the lab at Bart's. "You just weren't listening hard enough." / For blessedjessed on Tumblr for the Johnlock re-gifting.


**Notes:** This is for blessedjessed on Tumblr for the Johnlock re-gifting, who asked for the prompt "John can dance" with fluff/humor/romance/smut. I'm actually terrible with smut and I think it was meant to be cute and funny but it turned out a bit more like romantic serious fluff instead? If that's a thing. Sorry about that, and I hope this is all right for my first gift exchange, anyway…

Not britpicked, but my friend minuiko beta'd, so I want to lend her credit for being so wonderfully meticulous and honest in telling me when and why my writing sucked. Thank you!

* * *

(Exchange) (Step) (Waltz)

Jealousy was too pedestrian, though Sherlock found himself struggling to think of another term to define it; he knew, of course, that there was no romantic interest from either party, and that any emotional attachment that could push John into sharing a dance with Molly Hooper would only be motivated by a cloying sense of chivalry that came with that unwavering moral compass of his.

Besides, Molly had a new boyfriend – the young man standing in the corner talking to Donovan, just started his new position as a librarian last week, four younger siblings, dropped out of med school two years ago. John wasn't interested in a romantic affiliation with the woman, anyway. Sherlock knew it, he knew that he knew it, and still the sense of (wrongness) (greed) (possessiveness) wouldn't leave him.

"Sherlock," Lestrade said, flipping through the medical files he'd presented to him thirty-seven seconds earlier, "you're saying Payne was – "

"Hired by Richard M. Werner to kill Richard M. Werner, yes," Sherlock said, keeping his eyes on the figures in the centre of the room, dancing with the rest of the party's attendees. John danced as he did everything else: with a straight back and a charming smile, leading Molly gently across the floor as they exchanged polite conversation about, it seemed, her latest beau, though even from the side of the hall Sherlock could tell from the looseness of his limbs that John had had perhaps one too many drinks. Still, the movements were hypnotizing, somehow, the turns, the dips; Sherlock watched as John's hand curled around her waist. "Payne described the instructions he was sent as all typed, no verbal or face-to-face communication, so it's unlikely he would recognize his employer and target as one and the same. Werner was dying, had months to live. It's likely he figured he might make a quick go of it but pin the deed on someone he felt deserved it."

"His cheating partner," Lestrade muttered, letting out a long breath. "And she was deported immediately after the investigation discovered she didn't have citizenship. It's been fifty-six years – "

" – and considering she was forty-nine at the time of her boyfriend's murder I'd say the window of opportunity to question her has long passed."

"Right." Lestrade sighed, then shuffled the papers back in order and tucked them under his arm. "I'll go write this up, then. Thanks for the help."

Sherlock offered him a distracted grunt in reply.

"You didn't have to come tell me this," Lestrade said suddenly, and it made Sherlock turn; there was something knowing in his gaze that immediately rankled his defences. "You could've texted. Normally you don't bother responding until I ask you for an update myself – "

"I've come to collect John," Sherlock replied shortly. "He's needed at Baker Street and wasn't answering his phone." That much, at least, was true.

"Experiment gone wrong that you want him to clean up?"

Sherlock turned and strode from his side, dipping his head as he passed under a dangling Christmas decoration. "Good night, Lestrade."

"Happy Christmas," Lestrade's voice called after him with a noticeable trace of amusement, but Sherlock ignored it in favour of manoeuvring in and out of other attendees, squinting in the dim lighting as he headed for John and Molly in the middle of the room. He slid up to John's side and gripped the edge of his jacket sleeve.

"Time to take our leave, I should think," he said.

"I – Jesus, Sherlock, when did you get here?" John's faced was flushed, rosy, and he was looking far too nonchalant about his flatmate showing up to announce their departure from the Yard's Christmas party: two drinks over an hour and a half, washed it down with a glass of eggnog, was considering one last whiskey before leaving.

"Three minutes ago. Good evening, Molly."

"Hi, Sherlock," Molly said, looking pleasantly confused. She released John's hand to tuck a piece of hair behind her ear from where it had tangled in her bauble-shaped earring. "Is everything alright?"

"Grand," he said shortly. "John is needed at home. Come along, let's go."

"I – wait, Sherlock, the song's not through," John said, swaying a bit to the music drifting from the speakers across the room with his hand still on Molly's waist. "Can it wait? It's just a dance."

_I know that, why do you think I don't know that,_ he wanted to blurt out, but instead replied, "If you stay any longer you'll be tempted into another drink and need a police escort to accompany you home." He tugged a little more firmly on John's sleeve, poorly concealing his impatience. "I'm here to offer an alternative to that scenario." Sherlock, for a moment considering the diction of his next words, lowered his voice to add, "Prevent a public display of Watson intoxication, as it never seems to turn out for the best."

"God," John said, though to Sherlock's relief he looked neither frustrated nor annoyed, another benefit of tweaking him in the right direction when he was already loosely inebriated. "All right, fine. Maybe it is time to call it a night." He took Molly's hand again, patted it, and said, "Sorry for dashing. Have a lovely Christmas, Molly. Thanks for the dance."

"Oh – you're welcome," she said. "Evening, Sherlock. I'll see you around Bart's, then?"

Sherlock nodded and turned without a word, still gripping John's sleeve as he strode toward the door. John jogged to keep up with him for the first few steps before Sherlock let go; he waved to Dimmock before collecting his coat, bumping into a few people as he squeezed through the door and followed Sherlock outside.

"Lestrade only invited us because we've helped out on so many cases," John said as they headed down the corridor. "Molly at Bart's with the bodies, me with you. We're not even on the force, it was kind of him."

Sherlock grunted, only stopping to hold a hallway door open for him.

"What's this about?" John tried again when they were headed down the main steps. "Why'm I needed at home?"

Sherlock kept his eyes forward as they strode out of the building and into the crisp winter air, didn't look at John when he raised an eyebrow at him, not when he flagged down a cab, not when they slid into its backseats.

When he could see John wasn't going to relent in his silent interrogation, he simply said, "You weren't answering your phone."

His flatmate scrubbed at his forehead with a hand and closed his eyes. "And that's reason to worry you enough into coming to collect me?"

"Hardly worrying. I only found it," he considered for a moment, "curious. And I had a murder to close with Lestrade, so I figured I could make the trip."

John let out a tight breath of air through his nose and turned to the window. Upon reflection, Sherlock probably wouldn't believe that as reason enough to rouse him from his roost at 221B, either; he had arrived with the intention of delivering his notes and departing before any Yarders could engage him in conversation for the sake of holiday courtesy, but he could hardly explain something he was still having trouble classifying himself.

It wasn't as if he was interested in that sort of thing. Couldn't be. He had nothing to fear from Molly, or from any of the other women John so casually interested himself in. He was still reluctant to call it jealousy, hardly, but he couldn't help thinking of taking her place (he could see it in his mind's eye, they'd have to accommodate for his height but John could adapt, always would), however odd the picture seemed. It wasn't entirely unwanted, but only bizarre, enough to make him pause.

Frustrating. And this – whatever it was – just the tiniest bit troublesome uneasing concerning. Would require further investigation.

* * *

"You can dance," Sherlock declared when they arrived at 221B.

"Technically I suppose everyone _can_ dance," John replied, shrugging out of his coat and hanging it on the rack by the door, "but I know a thing or two, I suppose."

"You danced with Molly."

"It's odd hearing you state the obvious, you know," John said. He moved to the fireplace and fiddled with the grate for a few moments before a fire arose in the hearth, and he sank into his armchair with a long sigh, closing his eyes.

"I would like," Sherlock said, deliberately slow so as to not be misunderstood, "to reconstruct similar circumstances. Here."

John opened his eyes; they were a pleasant sort of tired, the lids lowered. The drinks must be catching up with him. "With me."

"Who else?" Sherlock dumped his coat on the couch and stood in the center of the floor. "Come on."

John looked at him. "What's this, then?"

He didn't think _"Testing a hypothesis,"_ would be well received, so Sherlock said, "It's Christmas," and hoped John's suspicion and self-restraint would take a vacation long enough for his curiosity and good humour to indulge him.

It didn't. John only stifled a yawn and looked thoughtful. "You want me to dance with you."

John was well aware of how much he loathed repeating himself; Sherlock frowned, nostrils flaring, and barely resisted the overwhelming urge to stomp his foot in impatience, or perhaps just drag him to his feet and go for it himself.

John started to uncurl himself from the chair, elbows resting on his knees, but didn't stand. "Experiment?"

"Social proposition."

"Why?"

_Because you wouldn't agree to this if you were completely sober, you'd protest about how it would be perceived by an outside party or go on with an unnecessary monologue about how you aren't gay _– any variation of any reasoning Sherlock could offer wasn't likely to motivate John further, so he stayed quiet.

John didn't move. "You should ask Mrs. Hudson, in that case. I'm sure she'd be thrilled if you asked as politely as you are now."

"No," Sherlock said, "the results would become corrupted."

"Sherlock."

"_John_."

John watched him for a long breath, and Sherlock lifted his chin in response. Finally, recalling a moment earlier in the evening, he lowered his voice a bit and said quietly, "It's just a dance."

The corner of John's lips twitched. Finally (_finally_) he stood and made to take his position, but paused. "We need music. Real dancing needs music."

"Use your imagination."

John hesitated for half of a second, but curled one hand over Sherlock's shoulder, fingers brushing his neck, and Sherlock took the other with his own. He recalled dancing lessons from his childhood, of course, knew the steps and could fall into the motions with a practiced ease, but none of his instructors had taught him how to dance with a man who was used to leading as well; the first few steps were a bit mismatched, disorienting as they both struggled to determine who was to move where.

"Am I allowed to talk during this?" John asked him when they'd managed to settle into a comfortable pattern of steps and movements, halfway between some sort of waltz and a disoriented shuffle.

"Yes." One hand was holding onto John's in a firm grip, the other softly clutched onto his jumper. John's hands, as always, were steady.

John swallowed, eyes flickering across the room, and then offered, "My phone ran out of battery. That's why I didn't answer your messages."

"I presumed as much," Sherlock said. "You always reply, even after a row. If you had been unable to reach your phone, in a public setting with a room full of police officers, Lestrade or another individual you trust on the force would have contacted me let me know something was wrong. The only conclusion was that your mobile was out of commission and you had consumed enough alcohol not to care but not enough to be escorted home."

"Mm." A corner of John's mouth lifted, but he kept his eyes beyond Sherlock's back, as if finding humour in something he couldn't see. "How was the case for Lestrade?"

"Werner was dying. Brain tumour. Hired a hitman to murder him, pinned it on his unfaithful girlfriend. Wasn't enough evidence to convict her, but investigation turned up her illegal citizenship and she was deported. I thought it odd Payne's employer gave him such specific instructions for him to shoot directly in the right cerebral hemisphere, as it turns out, right where the tumour was located – a sense of personal irony. The wife didn't know of his condition, so the directions must have come from someone who did. Simple."

"Everything's simple once it's solved." John's head had dipped to Sherlock's shoulder (exhaustion; it was nearly midnight and he's been awake since five-thirty in the morning, nightmare, couldn't go back to sleep, then a long day at the surgery, then he couldn't decline Lestrade's generous offer to the party) and he hummed, as if he was only half paying attention, which made Sherlock pause. He could see every strand of blond hair from this angle, the yellow and brown and the short, prickly ones on the back of his neck. He could tell John hadn't combed this morning, would consider getting a haircut within the week but would decide against it until next month, likely for some date or other.

"We do need music," John mumbled.

Sherlock hmmed, busy counting the freckles he could see on John's neck.

"I may be a bit drunker than I thought," John muttered, as if to himself. "I may do something stupid soon."

"Wouldn't be the first time," Sherlock said. They were pressed so close that even with John's head down Sherlock could tell he was biting his lip, feel him breathe on his neck.

"Sherlock," John said with his usual tone of exasperated fondness, "why'd you ask me to dance?" His hand curled around a little tighter on his neck, comfortable, familiar. He swayed, just a bit, as Sherlock led them in a turn.

"You danced with Molly," he repeated.

"You've said that."

"It's my answer."

"You usually offer evidence that's a bit more," John paused, "scientific. Um. Reasonable."

Sherlock had no response to this, but he slowed, anyway, at the feeling of John's lips against his neck.

He felt his jaw tighten a bit, an automatic reflex. Sherlock swallowed. "John?"

"There's the something stupid," he thought he heard John say before he pulled back. "Sorry. Think I'm going to call it a night."

There was something stuck in Sherlock's throat, maybe a cough or a word or two; but he didn't know, needed further time to study it, a new facet to this (fellowship) (affiliation) (exchange), pick it apart and put it back together, and so he let John leave his arms, turn away, exit the room in silence.

Theory demonstrated insufficient data. There was something else, an inconsistent variable, something he couldn't put his finger on, and he needed to think.

* * *

It was one in the morning. Sherlock was playing. Bach's Chaconne, Partita No. 2. The fire had nearly burned itself out, only smouldering embers in the hearth. John was asleep, or had at least been lying very quietly in his bed for the past twenty-three minutes.

Sherlock's neck still tingled where John's mouth had been less an hour ago, a ghost of a touch.

He wasn't sure if he liked it. He didn't _do_ things like – _this_, things like romance and feelings and emotional entanglements, things that ended in jealous murders and fake suicides and _marriages_, god, the tedium, but –

He had no frame of reference, no scale of comparison. The dance had proven nothing other than that John was unaccustomed to letting a partner lead, that his barber would be getting business within the next few weeks, that Sherlock could stare at John's hair, his skin, his eyes, and never run out of things to discover.

Outside, there was a teenage couple walking down the street on the pavement, leading each other home. They passed underneath a lamppost and with the added benefit of the orange light Sherlock could determine _year thirteen, together less than a fortnight, met through her brother's rugby team, she'll be traveling to Edinburgh for the holidays_, and that even seventeen-year-old teenagers, somehow, could understand this whole _– caring _business better than he could.

John had kissed him. His neck. John had, in some way or another, looked at Sherlock's skin and thought _I'd like to put my lips there_, and done so. John had been slightly drunk but, for a moment, felt the same curiosity in the pit of his being, the same desire to explore a small patch of skin, and went for it. The evidence still tingled on his skin, a reminder, or a warning.

Sherlock decided that he liked it.

John was awake. He could sense someone moving upstairs, quiet shuffling. To the bathroom? Down the stairs. _No, _he thought furiously, making a particularly long whine on his violin, _don't come downstairs, let me have a few minutes more –_

"Sherlock?"

He responded with a loud trill, kept his eyes staring as the two outside headed down the street and out of the lamppost's bubble of light, now swallowed by the darkness.

"I had few glasses of water from the tap. To sober up. I want to apologize for, ah. Before."

Sherlock let his violin do the talking.

John grew quiet, listening to the piece for a polite minute, before trying again. "Sherlock."

Sherlock raised the bow from the strings but didn't move the instrument from his neck. "Why?"

"Pardon?"

"Why apologize?" He deposited the violin in its case on the table and turned to John, brandishing the bow like a teacher's pointing stick. He blinked, then lowered it. "You're ashamed."

"What? No, I – " John looked frazzled, frustrated, and took a breath before beginning again. "I just realized it made you uncomfortable. And I know – I remembered, that night at Angelo's, what you said."

The night of their first case. What had he said? _Married to my work_, _flattered but not interested_, right, of course.

"Dismiss it," Sherlock said.

"Dismiss – what?"

"Forget Angelo's, forget the conversation." Sherlock took a step forward, eyes on John's, noting the way he kept glancing at the violin to avoid looking at him. "What would you be saying right now? What would you be doing?"

"I," John tried. "Sherlock, this isn't the discussion I really wanted to have when I came down – "

"You wanted to apologize, remove this from your conscience because of your assumed notions of my romantic interest or lack thereof conflicting with what occurred earlier this evening. You'd then head upstairs, spend two hours trying to sleep, in which you wouldn't succeed, making you cranky and uncomfortable around me likely for the rest of the day," Sherlock declared, "which isn't acceptable. So we're having this conversation now."

"Sherlock," John said, and (ah!) there was that familiar look of frustration-borderline-exasperation he donned whenever Sherlock overstepped some social boundary or other. But Sherlock didn't particularly care – finally, with John getting emotional and therefore reckless with his language, they could get somewhere. "Please. It was a mistake. Can we let it go?"

"No, and you're not forgiven," Sherlock said. "I need you here."

"What?" John's eyes were now scrunched in confusion – no, anger, his fists were clenching – and he looked about ready to storm off or start yelling. Neither of which were preferable options, so –

"To sort it out," he said impatiently, flipping the bow through the air. "_This_ out."

"Sort _what _out? I'm sorry for it, Sherlock, I am, clearly it's thrown you for a loop, so let's just – go to bed, get a good night's rest. I won't bother you in the morning, if that's what you're concerned with."

_Wrong, wrong, wrong!_ Sherlock let out a huff of air through his nose; John wasn't getting it, couldn't _see_, and god, he was wasting his breath.

"I told you to forget Angelo's," Sherlock said again. "The conversation never happened. How would you follow up to what happened an hour ago?"

"I – wouldn't." John frowned. "It wasn't appropriate, anyway. I'd drop it and move on, if you'd just agree to_ do the same_."

"And what if I didn't?" Sherlock questioned. "Agree to do the same. I want to talk about this."

"I don't – " John cut himself off, closed his eyes. Opened them again. "I don't know. I don't think it matters."

"It does to you. This sort of thing." _Your area of expertise_, he didn't say.

"I just don't want you overanalyzing it, treating it like a specimen, when it didn't mean..." John drifted off. He took a breath and tried again, "When it was a mistake."

Sherlock tapped his bow idly against his leg. Looked at the mirror hanging on the wall. John's reflection offered no answers, only the same mirrored apology. "You've said that."

"I mean it."

He swiveled back around. "No, you don't." The contradiction came automatically, startling, but Sherlock didn't take it back, because the look on John's face at those words told him all he needed to know.

"Fine." He looked at Sherlock squarely, as if daring him to comment further. "But while I'm here, another thing," John said suddenly, in one big rush. "Using my sister's alcoholism to manipulate me into being where you want – "

"It's not on," Sherlock finished as John said, "isn't all right." John blinked, but Sherlock continued, "For what it's worth, my comments were directed less in a reference toward your family's history of substance abuse and more as a. A cautious reminder."

"For you to lead me where you want me to go."

"For you to make your own conclusions on the evidence I've gathered."

John paused. Looked, suddenly, at Sherlock with a tightening in his brow, but some odd softness in his eyes. "This, all this isn't about earlier this evening."

Sherlock swallowed.

John frowned. "This is about something else."

That something was still caught in his throat, words or emotion or fallacy tangled in the pit of his stomach, awkward and uncomfortable. He set his bow over the violin case, careful. "I have another proposition."

"You do."

"I want you to do it again."

It seemed to be a night for pausing and hesitations. "Come again?"

"You apologized, but I don't forgive you because I'd like you to do it again. Wherever you like, I'm not fussy. I enjoyed the previous placement, however, if you were agreeing."

"If this is another of your experiments – "

"Less experimental, more." Sherlock stopped, searched for the right words, and tried again. "Proving something. If you'd be willing."

John looked at him. And Sherlock looked back, still trying to categorize that emotion threatening to rise up and swallow him whole, the one he could recognize on John's face, too: he had to put a name to it, wrap it up in a term he could understand, but it was starting to look, he suspected, that understanding would require a proper demonstration. Possibly several, provided John was accommodating.

"Please," Sherlock said.

John closed his eyes and sighed something that sounded like _"God,"_ and Sherlock took that as an invitation. He stepped around his armchair and strode forward across the room, to the doorway, to John, lips parting as John rose up to meet him halfway.

_Oh,_ Sherlock realized, and that (feeling) (sensation) (urge) he'd been examining clicked into place, assigned itself a spot in his mental database and lodged itself there, impossible and irreplaceable. _Oh._

When they parted, when his brain began buzzing and his mouth felt as if it wouldn't recover, John removed his hand from the back of Sherlock's neck, looking a bit surprised, a bit not.

"Did you. Ah. Did you prove whatever it was to yourself?"

"I did," Sherlock said quietly. "And to you, I should think."

John's lips didn't part when he smiled, but the corners of his eyes crinkled, the softness returning. It reminded him, inexplicably, of the night John had shot the cabbie. Sherlock could relate.

"You danced with Molly," Sherlock said for the third time that evening.

"And I danced with you after," John added, some question in his voice, pressing but not accusatory.

"I was curious."

"You came to pick me up from the Yard's party because you were jealous."

Sherlock didn't dignify this with a response, though privately, he still wasn't quite sure. Part jealously, perhaps, but also something more personal, less about Molly; it was something he knew John knew, too, without having to say or talk about, something that perhaps didn't need a word.

John could dance. Sherlock knew the steps (_Technically everyone _can _dance_, John had said) but it seemed this, like so much else, was something beyond his capabilities, something everybody else just _got_ while he was left struggling with the vocabulary, for some understandable terminology, something provable, evidential.

"It's not rocket science," John said now, as if predicting where Sherlock's mental process was taking him (which, to be fair, he likely could; John's conclusions in these matters were usually based on instinct rather than reason, though to him that only added to their validity). "It's not something you can test or experiment with, you can't mark it so definitively."

_I know that now,_ Sherlock wanted to say, but instead: "You sound certain."

"After living with you for as long as I have, I think I should be." John leaned in again, gentle, as if he wasn't sure whether Sherlock would pull away; but Sherlock parted his lips again, pressed them to John's. That selfish something was still there, would likely never go away, but he indulged in it; catalogued John's scent, his taste, the little noises he made as Sherlock gripped his hip, pushed closer.

"We need music next time," John muttered. "Music goes with proper dancing."

"There was music." Had been music, really, and dancing, ever since John walked into that lab at Bart's. "You just weren't listening hard enough." Sherlock removed himself from John and picked up his violin and its bow, lifting the body to his neck as he stepped to the window again. John looked marvellous against the light from here, the best definition of familiar, reliable, steady. Sherlock could imagine his own silhouette in the window, how he would look in comparison to John: he knew he made a striking figure at the best of times, an intimidating or relentless one at worst, but John was looking at him, as always, as if he thought neither. Like Sherlock was something else, something brilliant and extraordinary that made him feel like standing a little taller, holding his head a little higher.

"Unless you plan to dance solo, you may want to have a seat," Sherlock told him, gesturing at the couch. "I was just getting started." He turned back to the window, looking out again at a deserted two a.m. Baker Street, and closed his eyes.

"Me too," John said suddenly, warmly. His voice was much closer, coming from the armchair, instead. So open, as always, in acknowledging this silent (exchange) (step) (waltz) that had begun in Bart's lab – and it would continue, Sherlock expected, long after they were done with any and every verbal conversation in present and future. "This whatever it is. I'm sure you knew that. But me, too."

Variable deemed indefinable, but acceptable results still produced. Further study to be continued.

Sherlock allowed himself a private smile, lifted the bow to the strings, and played on.

* * *

**Notes:** The cold case Sherlock solves for Lestrade was loosely based on the one in Ep9 of CBS's Elementary. Thanks for reading!


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